Alcatel-Lucent 7710 SR OS, Interface Configuration Manual

Page: 35 / 436

Interface Configuration
7710 SR OS Interface Configuration Guide Page 35
FRF.12 End-to-End Fragmentation
The user enables FRF.12 e2e fragmentation on a per FR SAP basis. A fragmentation header is
added between the standard Q.922 header and the payload. This header consists of a 2-byte
Network Layer Protocol ID (NLPID) of value 0xB1 to indicate e2e fragmentation payload and a
2-byte containing the Beginning bit (B-bit), the End-bit (E-bit), the Control bit (C-bit), and the
Sequence Number field.
The following is the mode of operation for the fragmentation in the transmit direction of the FR
SAP. Frames of all the FR SAP forwarding class queues are subject to fragmentation. The
fragmentation header is, however, not included when the frame size is smaller than the user
configured fragmentation size. The SAP transmits all fragments of a frame before sending the next
full or fragmented frame. The fragmentation threshold is configurable in the range 128 — 512
bytes. In the receive direction, the SAP accepts a full frame interleaved with fragments of another
frame to interoperate with other vendor implementations.
A FR SAP with FRF.12 e2e fragmentation enabled can be part of a VPLS service, an IES service,
a VPRN service, an Ethernet VLL service, or an IP VLL service. This SAP cannot be part of a FR
VLL service or an FRF.5 VLL service. However, fragmented frames received on such VLLs will
be passed transparently as in current implementation.
FRF.12 UNI/NNI Link Fragmentation
The user enables FRF.12 UNI/NNI link fragmentation on a per FR circuit basis. All FR SAPs
configured on this circuit are subject to fragmentation. A fragmentation header is added on top of
the standard Q.922 header. This header consists of 2 bytes containing the beginning bit (B-bit), the
End-bit (E-bit), the Control bit (C-bit), and the sequence number field. The fragmentation header
is included on frames of all SAPs regardless if the frame size is larger or not than the fragment
size.
The FECN, BECN, and DE bits of all fragments of a given FR frame are set to the same value as
the original frame. The FECN, BECN, and DE bits of a re-assembled frame are set to the logical
OR of the corresponding bits on the constituent fragments.
The operator must delete all configured FR SAPs on a port before enabling or disabling FRF.12
UNI/NNI on that port. Also, the user must shut down the port in order to change the value of the
fragmentation threshold.
A FR SAP on a FR circuit with FRF.12 UNI/NNI fragmentation enabled can be part of a VLL,
VPLS, IES, or VPRN service.
QoS for a link with FRF.12 UNI/NNI fragmentation is the same as for a MLFR bundle. The FR
class queue parameters and its scheduling parameters are configured by applying an egress QoS